Method for manufacturing porous structure and method for forming pattern

Abstract

A pattern forming material contains a block copolymer or graft copolymer and forms a structure having micro polymer phases, in which, with respect to at least two polymer chains among polymer chains constituting the block copolymer or graft copolymer, the ratio between N/(Nc−No) values of monomer units constituting respective polymer chains is 1.4 or more, where N represents total number of atoms in the monomer unit, Nc represents the number of carbon atoms in the monomer unit, No represents the number of oxygen atoms in the monomer unit.

1. A method for manufacturing a porous structure, comprising:
 forming a molded product consisting of a pattern forming material comprising a copolymer selected from the group consisting of a block copolymer and a graft copolymer; 
 the block copolymer and the graft copolymer each having:
 a first polymer chain whose main chain may be cut by irradiation with an energy beam selected from the group consisting of an electron beam, a γ-ray beam, and an X-ray beam, and 
 a second polymer chain which does not decompose upon irradiation with the energy beam; 
 
 forming a microphase-separated structure in the molded product; the structure comprising:
 an energy-beam-decomposable polymer phase comprising the first polymer, and 
 a remaining polymer phase comprising the second polymer; 
 
 cutting the main chain of the first polymer in the microphase-separated structure by irradiating the molded product with the energy beam; and 
 forming a porous structure comprised of the remaining polymer phase by etching and selectively removing the energy-beam-decomposable polymer phase; 
 wherein the copolymer is made self-supporting prior to the etching and selectively removing the energy-beam-decomposable polymer phase. 
 
     
     
       2. The method according to  claim 1 , wherein the polymer chain whose main chain is cut by irradiation with an energy beam is a polyalkylmethacrylate chain. 
     
     
       3. The method according to  claim 1 , wherein the polymer chain whose main chain is cut by irradiation with an energy beam has a molecular weight of 100,000 or less, and wherein the copolymer has a molecular weight distribution (Mw/Mn) of 1.20 or less, and wherein the molecular weight ratio between the indecomposable polymer chain and the decomposable polymer chain is ranging from 75:25 to 90:10. 
     
     
       4. The method according to  claim 1 , wherein the copolymer has a molecular weight of 50,000 or more and has a molecular weight distribution (Mw/Mn) of 1.15 or less, and wherein a molecular weight ratio between the indecomposable polymer chain and the decomposable polymer chain is ranging from 75:25 to 90:10. 
     
     
       5. The method according to  claim 1 , further comprising using the porous structure as at least part of a separator of an electrochemical cell comprising a pair of electrodes and a separator interposed between the electrodes and impregnated with an electrolyte. 
     
     
       6. The method according to clam  5 , wherein the porous structure has an aggregated structure of domains, the domains having a radius of gyration of 50 μm or less in which unit cells having a radius of gyration from 10 to 500 nm are periodically arranged. 
     
     
       7. The method according to  claim 1 , further comprising using the porous structure as a hollow fiber filter. 
     
     
       8. The method according to  claim 7 , wherein the porous structure has an aggregated structure of domains, the domains having a radius of gyration of 50 μm or less in which unit cells having a radius of gyration from 10 to 500 nm are periodically arranged. 
     
     
       9. The method according to clam  1 , wherein the porous structure has an aggregated structure of domains, the domains having a radius of gyration of 50 μm or less in which unit cells having a radius of gyration from 10 to 500 nm are periodically arranged. 
     
     
       10. The method of  claim 1 , wherein the molded product is formed by at least one of hot press molding, injection molding and transfer molding. 
     
     
       11. The method of  claim 1 , wherein the molded product is formed by melting and molding the copolymer in the absence of a substrate. 
     
     
       12. The method of  claim 1 , further comprising:
 filling the pores of the porous structure with an inorganic substance. 
 
     
     
       13. The method of  claim 12 , wherein the inorganic substance is filled by at least one of plating or chemical vapor deposition. 
     
     
       14. The method of  claim 1 , wherein the molded product is a fiber formed by extrusion molding the copolymer.